1. Field of the Invention
The present invention generally relates to fluid handling devices, their uses and operation. More particularly, this invention relates to a fluid delivery system and method that utilizes a resonating tube to deliver a fluid and monitor multiple parameters of the delivered fluid.
2. Description of the Related Art
Infusion therapy generally involves the administration of a medication to a subject using intravenous (IV), subcutaneous and epidural routes. A wide variety of fluid infusion pumps have been developed over the years that are capable of delivering a precise amount of medication at a controlled rate. Such pumps include elastomeric, gravity fed, syringe, electrical and mechanical pumps. Valves and flow sensors have been incorporated into some infusion pump designs to improve dosage accuracy and to control the flow of fluids (e.g., drugs, medications, etc.) through these systems. More recently, micromachined flow sensors, valves and pumps have been developed, some of which have been used in medication and drug delivery applications.
Certain types of infusion therapies require extremely small amounts of fluids to be delivered in a very precise manner. However, the accuracy of infusion pumps typically range from about +/−15% for volumetric pumps, down to about +/−3% for syringe pumps. Coriolis mass flow sensors can provide flow rate measuring accuracies of under +/−1%. However, their high cost and general requirements for relatively high flow rates have restricted their use in the medical field.
Another aspect of fluid delivery systems, both within and outside the medical industry, is the prevention of gas bubbles from being delivered with the fluid. It is well known that trapped gas bubbles in the blood stream can lead to stroke or death. Because of this, IV infusion pump systems have widely employed gas bubble detectors that ultrasonically detect gas bubbles in a fluid prior to its delivery into the blood stream. An ultrasonic sensor of this type employs a transmitter and receiver positioned on opposite sides of a fluid-carrying duct, and detects a change in ultrasonic wave transmission if bubbles are present in the fluid flowing between the transmitter and receiver.
Yet another aspect of infusion therapy and various types of fluid delivery systems used outside the medical industry is the ability to sense if fluid blockage occurs. For this purpose, pressure sensors have typically been used to detect the increase in pressure that occurs as a result of an occlusion or blockage downstream of a pump. In IV infusion pump systems, two pressure sensors are often used, placed upstream and downstream of the infusion location, to monitor blockage.
In view of the above considerations, IV infusion pump systems have often employed four separate sensors: two pressure sensors to monitor blockage, an ultrasonic device to detect gas bubbles, and a flow sensor to measure fluid flow. It would be advantageous if the number of separate devices required to perform these functions could be reduced, while maintaining or improving the precision by which these functions are performed.